Perched on a hill top in Tuscany, Pienza was originally called Corsignano. Pope Pius II loved his hometown greatly and wished to transform it into a concrete example of his theories on the ideal city. For this purpose he hires the arhitect Bernardo Rossellino and gets directly involved in the planning. Influenced by Alberti’s writings, Pius plans to raise a uniform and self-sufficient city around the central square. Yet as he dies in 1462, the urban sketch of the city that takes his name stops there, with only 40 buildings finished. In the heart of the “ideal city”, Bernardo Rossellino had managed to implement a trapezoidal square, which represents the first attempt at urban renewal in the postclassical period.

The space is not large, yet the illusion of greater dimension is created through its shape and through the drawing of the pavement. The final effect is that of a scene bordered by important buildings. Palazzo Vescovile forms the east side. On the opposite side stands the papal palace. The city hall lies to the north and Rossellino chose a Florentine model for its tower. Two other buildings form the northern side next to the city hall. The square is dominated by the façade of the cathedral, built on the small side of the trapezoid, so that its dimensions are lessened in order to not end up overwhelming the square, for the Pope did not aim to build a city of monumental but of human dimensions. Everything was carefully calculated, and the construction of the church took the motion of the sun into account. Inspired by Austrian cathedrals bathing in natural light, the Pope asked that the church not respect the traditional west-east alignment, but to be set in such a way so that the sunlight might pour in from the southern windows. The church is lined with the tip of Mount Amiata, an extinct volcano. The southern windows of the church make its peak visible, but the peak itself is not visible from the square. This leads to an interesting perception reversal: the interior of the church creates the sensation of a wide open space towards the landscape, while the square barely offers access to surrounding nature, suggesting instead the feeling of an interior space. The two open and narrow spaces in the square, on the cathedral’s sides, are the first Renaissance examples of viewing rural landscapes from within a town. In this respect, it represents a break with traditional medieval squares. In order to see the landscape, one must reach the very end of the square.

Various details from the façade of a building reappear on another façade in the square, the rectangular shape of the façades is a scale copy of the shape of the windows. The windows at the upper level of the papal palace are one of Rossellino’s inventions, a combination between the Roman cross and the Tuscan rose window. The cross reappears as a detail on the windows of the Palazzo Vescovile and the rose window reappears in the design of the city hall’s windows. Archways and circular details, grouped in threes, repeatedly appear on the façade of each building, The travertine grid and the red brick pavement mirrors the series of compartments on the church façade and are lined with the pillars, doors and corners of all the buildings in the square. In the middle of the square there is a travertine circle, and the distance from the circle to the door of the church is equal to the distance from the base of the church to the occhio, the typical round window from the façade of the church. This is not the only “coincidence”, for the square respects a geometry that is based on the numbers 3, 5, 9. Moreover, it was found in the early 2000s that the shadow of the cathedral lines perfectly with the pavement grid in certain moments. Specifically, 11 days after the solar equinox. It was known already in the 15th century that there is a 11 day difference between the used calendar and the astronomical one. The calendar reform was highly controversial within the Catholic Church, since Easter is calculated according to the equinox. Pieper, who observed the lining of the church shadow with the grid, believes that the square was initially supposed to represent this on the very day of the equinox. Thus, the construction was began, but the project was reconstructed so that the alignment would take place on the official day of the equinox. When the modification was decided, the construction of the square buildings was already underway. Redrawing the pavement grid would have led to discrepancies with building details, so the only solution was found in further raising the roof of the cathedral. This is confirmed since the Albertian proportions on the church pediment are not respected. It is a mystery that the details of the reconstruction, as well as the story of aligning the cathedral’s shadow to the drawing of the pavement, make no appearance in the Pope’s extremely detailed diary.